1. Field of the Invention
The present invention relates to an apparatus and method for sorting particles, and more particularly, concerns an apparatus and method for sorting particles moving in a liquid stream, according to differences in particle parameters, by gas actuation.
2. Description of the Prior Art
Flow analysis of particles has been employed in the determination of characteristics of individual particles. Such analysis is most useful in analyzing characteristics of cells for the collection of information which would be useful in areas of research, hematology, immunology and the like. The researcher may be interested, for example, in determining specific characteristics of individual cells so that the cells may be classified, identified, quantified and then sorted for further investigations or analysis. There are a number of well-known cell analysis apparatuses available to the researcher at present utilizing flow cytometry techniques for the measurement of characteristics of individual cells. One such analyzer is known as the FACS.TM. Analyzer, sold by Becton Dickinson FACS Systems, Sunnyvale, Calif. Not all available analyzers utilized in flow cytometry, however, analyze the cells and then sort the cells into different categories.
One such sorting apparatus is disclosed by Zold in U.S. Pat. No. 4,175,662. Zold describes a method and apparatus which allows the sorting of particles or cells in accordance with their physical or chemical properties. Sorting is achieved after the particles are analyzed by reliance upon an electrolysis gas impulse which causes a deflection of the particle suspension stream to flow into a different channel. Particles in the different channel, having been sorted, may then be collected separately from particles flowing in the main channel. The method of sorting described by Zold is based on the direct changing of the liquid electrolyte flow path while the suspended particles are deflected only indirectly by the change of the liquid flow.
Application of the particle sorting technique similar to that described by Zold would add a desired improvement to those analyzers which do not have sorting capabilities. However, improvements in the technique as described by Zold would be required in order to assure the compatability of the analyzing features with the sorting features in a flow cytometric apparatus which both analyzes and sorts cells or other particles. It is to such an improvement that the present invention is directed.